Subcaliber projectile and sabot



y 1956 G. B. SHOBER SUBCALIBER PROJECTILE AND SABOT Filed Oct. 12, 1964 mwm uz 3am INVENTOR. GEORGE B. SHOBER m zamkywu N N V ATTORNEY a spin stabilized projectile.

United States Patent 3,262,391 SUBCALIBER PROJECTILE AND SABOT George B. Shober, Philadelphia, Pa., assignor to The Budd Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Oct. 12, 1964, Ser. No. 403,311 Claims. (Cl. 102-93) This invention relates to improvements in subcaliber projectiles or missiles fitted with sabots. While not'limited thereto, the invention is particularly applicable to gunlaunched, high-altitude probes.

Probes are devices in the shape of subcaliber projectiles that carry suitable instrumentation for probing high altitudes. The probes are launched or fired from a gun at substantially 90 elevation and reach altitudes in the order of 250,000 ft. and higher. To develop the pre requisite high velocities for achieving such high altitudes, the probes are fitted with sabots that are discarded upon firing. One form of prior art sabot comprises three or four metal segments that extend completely around the projectile, but such a sabot is disadvantageous because the segments are lethal upon falling to the earth after firing and discard. Accordingly, one of the objects of the invention is to provide a sabot that is non-lethal upon falling to the ground after firing and discard.

Another object is to provide a multi-segment sabot comprised of a multiplicity of lightweight segments or discards that have low terminal velocity characteristics in free fall.

Still another object is to provide a sabot and projectile that are constructed so that each stands an equal chance of structural failure during firing.

Other objects and advantages of the invention will be apparent from the following description taken in connection with the accompanying drawing wherein:

FIG. 1 is a side elevational view of a probe embodying the invention;

FIG. 2 is a transverse sectional view, on an enlarged scale for clarity of illustration, taken along reference lines 2-2 of FIG. 1;

FIG. 3 is a longitudinal sectional view, with portions removed, along reference lines 33 of FIG. 2;

FIG. 4 is an enlarged exploded viewof a detail; and

FIG. 5 is a perspective view of a modified form of a discard.

Referring now to the drawing, there is shown in FIG. 1, a probe that comprises a subcaliber projectile fitted with a segmented gas seal 11 and a sabot 12 held in place by a cartridge case 13, shown in phantom for simplicity of illustration. The cartridge case is adapted to be filled with a propellant charge which, upon ignition, propels the projectile 10, seal 11, and sabot 12 through a smooth bore gun tube inconventional manner.

Projectile 10 comprises an elongated body 14 having a nose 15 and a boom or tail fitted with a plurality of stabilizing fins 16. The projectile is axially symmetric and is considered to be a non-spinning type since it is not At approximately its longitudinal center, body 14 is provided with a plurality of longitudinally-spaced, circumferentially-extending teeth 17.

Seal 11 is of any conventional type and may comprise a polyethylene portion 1 1a abutting a frangible, hard rubber portion 11b. The outer diameter of the seal is approximately the same as that of the gun tube. The trailing face of portion 11a is provided with a rearwardly opening annular groove 19 that provides two flexible radially spaced inner and outer lips adapted to be urged by the gas pressure developed during firing into tight sealing engagement with both the projectile body 14 and the interior of the gun tube. The leading edge of the front portion 11b of the seal is provided with an over hanging lip 20 that engages the rear edge of sabot 12 and thereby transmits thrusts developed by the gas acting on seal 11 into the sabot in a manner more fully described hereafter. Upon firing, seal 11 is blown off the projectile when the projectile leaves the gun tube.

Sabot 12 comprises a multiplicity of segments or discards 21. As shown in FIG. 2, the discards are wedge shaped in transverse cross section and, as shown in FIG. 3, the discards 21 are substantially trapezoidal when viewed from the side. Each discard 21 has a toothed inner edge 22, an outer edge 23 that is shorter in length than edge 22 and bevelled leading and trailing edges 24 and 25, respectively. Inner edge 22 has a plurality of longitudinally spaced teeth 26 engaged or meshed with teeth 17 of projectile 10 for transmitting thrust thereto.

With reference to FIG. 4, each tooth 17 comprises a top land 17a bounded by a leading edge 17c and a trailing edge 17d. A bottom land 17b extends between the leading and trailing edges of adjacent teeth. Similarly, each tooth 26 has a top land 26a bounded by leading and trailing edges 26c and 26d respectively. A bottom land 26]) extends between adjacent teeth. The teeth are shaped complementarily so that the top and bottom lands of each tooth 26 are adjacent to the bottom and top lands respectively of each tooth 17 and so that the leading and trailing edges of each tooth 26 abut the trailing and leading edges respectively of each tooth 17.

Preferably, body I14 is steel and the discards are a lightweight metal alloy, such as a magnesium alloy. To compensate for the difference in strength between such materials and to insure that teeth 17 and teeth 26 have an equal chance of failure during firing, the thickness of each tooth, measured at its base, ie, a line extending between the bottom lands boundingeach tooth, is inversely proportional to the yield strength of the material. Thus, the thickness of teeth 26 are greater than those of teeth 17 because the magnesium alloy has a lower yield strength than that of the steel.

Lip 20 of seal 11 engages the trailing bevelled edge 25 of each discard 21. Since the bevelled edge is at an angle relative to the axis of the projectile, the thrust imparted to each discard 21 from the gas seal during firing, has a longitudinal component that impels the projectile from the gun tube and a radial inward component that holds discard 21 in engagement with the teeth 17 of body 14. After leaving the gun tube, the pressure of the air hitting sabot 12 causes the discards to fly off. To aid this release of discards 21, the leading edge 26c and trailing edge 26d depart from the normal a slight amount, for example 7, so that teeth release readily.

Each discard is dynamically unstable in free fall after being discarded. To achieve this, each discard has a relatively high area-to-weight ratio and it is substantially flat so that it tends to rotate about a longitudinal extending axis 28 in free fall, the axis being located approximately as shown in FIG. 3 between inner and outer edges 22 and 23. In free fall, such rotation produces a high aerodynamic drag that results in a low terminal velocity that is well below a lethal velocity. Such rotation also produces a certain amount of lift whereby as the discard falls downwardly it also follows a spiral path due to the lift component. To achieve the high area-to-weight ratio, the discards are relatively thin and are numerous. Preferably, the radial inner edge of'each discard is in the order of A of an inch so that for a three inch diameter projectile, there would be approximately discards. In comparison, the prior art sabots were relatively few in number and have a low area to weight ratio so that they are in the nature of unsymmetrical projectiles that fall in a somewhat haphazard fashion by tumbling and rolling but had a relatively great terminal velocity and are lethal.

The discards can be any one of a variety of shapes. As an alternate form, FIG. 5 shows a discard 21' stamped from uniformly thick sheet metal so as to have a shape similar to that of discards 21. Discard 21 has a longitudinally extending spacing bead '29 that is adapted to nest against adjacent spacing beads of other discards 21' so as to angularly space the outer edges of the discards whereby the discards extend radially relative to the axis of the projectile. If desired, the spacing between such discards can be filled with some form of a suitable frangible plastic that disintegrates upon firing.

While the invention is illustrated as applied to a specific probe, it is to be understood that it is applicable to other subcaliber projectiles and that the invention is not to be 7 limited thereto except as defined in the appended claims.

What is claimed is:

'1. The combination comprising: a subcaliber projectile having an elongated body provided, at its midsection, with a plurality of teeth; a gas seal fitted on said body rearwardly of said teeth; and a sabot fitted on said body in front of said seal in engagement therewith for receiving thrust from said seal and transmitting it to said body, said sabot comprising a multiplicity of substantially flat, radial discards having teeth engaged with the teeth of said body for transmitting thrust thereto, said seal having an inclined surface and said discards having bevelled edges abut-ting said inclined surface, whereby thethrust transmitted therebe-tween has a longitudinal component for .impelling said projectile forwardly and a radial inward component for holding said teeth of said discards in en gagement with the teeth of said body, said teeth of said 4 discards and of said body having base thicknesses inversely proportional to the yield strength of their respective materials.

2. In the combination of 1 wherein said gas seal includes a forwardly extending lip portion overhanging the toothed portion of said body to retain said discards therebetween, and wherein said inclined surface constitutes the lower bounding surface of said lip portion.

3. -In the combination of claim 1 wherein each of said multiplicity of discards is in the form of a generally plane figure having two parallel sides, one longer than the other, and two non-parallel sides, said teeth of each said discard being disposed along the longer of said parallel sides.

4. In the combination set forth in claim 3 wherein said discards are wedge shaped, in radial cross section relative to the longitudinal axis of said body, each discard being of lesser thickness along its longer parallel side.

I 5. In the combination set forth in claim 3 wherein each discard includes a beadlike deformation disposed in parallel relationship relative to its longer non-parallel side whereby said multiplicity of discards are enabled to be retained in nested relationship about the periphery of the threaded portion of said body.

References Cited by the Examiner UNITED STATES PATENTS 3,107,615 10/1963 Brady 102--93 X BENJAMIN A. BORCHELT, Primary Examiner.

R. F. STAHL, Assistant Examiner. 

1. THE COMBINATION COMPRISING: A SUBCALIBER PROJECTILE HAVING AN ELONGATED BODY PROVIDED, AT ITS MIDSECTION, WITH A PLURALITY OF TEETH; A GAS SEAL FITTED ON SAID BODY REARWARDLY OF SAID TEETH; AND A SABOT FITTED ON SAID BODY IN FRONT OF SAID SEAL IN ENGAGEMENT THEREWITH FOR RECEIVING THRUST FROM SAID SEAL AND TRANSMITTING IT TO SAID BODY, SAID SABOT COMPRISING A MULTIPLICITY OF SUBSTANTIALLY FLAT, RADIAL DISCARDS HAVING TEETH ENGAGED WITH THE TEETH OF SAID BODY FOR TRANSMITTING THRUST THERETO, SAID SEAL HAVING AN INCLINED SURFACE OF SAID DISCARDS HAVING BEVELLED EDGES ABUTTING SAID INCLINED SURFACE, WHEREBY THE THRUST TRANSMITTED THEREBETWEEN HAS A LONGITUDINAL COMPONENT FOR IMPELLING SAID PROJECTILE FORWARDLY AND A RADIAL INWARD COMPONENT FOR HOLDING SAID TEETH OF SAID DISCARDS IN ENGAGEMENT WITH THE TEETH OF SAID BODY, SAID TEETH OF SAID DISCARDS AND OF SAID BODY HAVING BASE THICKNESSES INVERSELY PROPORTIONAL TO THE YIELD STRENGTH OF THEIR RESPECTIVE MATERIALS. 